Field of Invention
The present invention relates to a twin rotor housing assembly for a combine harvester comprising a pair of curved cover plates which each form part of a generally cylindrical rotor housing for a respective rotor, and each comprising, along a longitudinal edge, means to secure the cover plates to a central fixing structure.
Description of Related Art
Twin axial-flow or rotary combine harvesters usually have a pair of crop processing rotors each arranged side by side and each having a rotation axis which is substantially parallel to the longitudinal axis of the harvester. In some machines the rotors perform both the threshing and separating action upon the cut crop flow delivered thereto. In other machines, such as ‘hybrid’ machines, a tangential-flow threshing cylinder is employed upstream of the rotors, wherein the rotors themselves serve a subsequent separating function.
Each crop processing rotor is mounted in a respective rotor housing which is generally cylindrical and which includes a grate or concave in the lower section to allow separated grain to fall onto an underlying collection pan. Enclosing curved cover plates are provided in an upper section of the housing.
Crop material is fed into a front inlet section where the crop material is engaged by flighting elements on the rotor. The crop material is conveyed as a ribbon or mat in a generally rearward axial and helical path in the space between the rotor and the rotor housing. Axial conveyance of the crop material is driven by the interaction between guide vanes provided on the inside surface of the upper cover plates and threshing and separating elements provided on the rotor. Threshing of the crop material and the subsequent separation of the grain therefrom is mostly carried out in the lower portions of the helical path by the interaction between the threshing and separating elements respectively and the concave, the space between which is adjustable. Separated crop material passes by gravity through the grate whereas the longer bulkier straw residue is conveyed via an outlet or discharge section at the rear of the housing.
The pair of rotor housings together provide a housing assembly which is secured with respect to the frame or chassis of the combine harvester. The upper cover plates and the lower concave sections are separately mounted components.
The cover plates are substantially half cylindrical in shape and are mounted along respective outer and inner longitudinal edges to fixing points provided by the machine frame. Flanges are often provided along the edges of the cover plates so as to provide means of fastening to the frame by bolts.
There is a continuing demand for combine harvesters of larger and larger capacity. However, constraints on the overall machine size dictated by national highway laws prevent manufacturers from simply upping the dimensions of the various crop processing systems. For example, the diameter of the rotor housings of twin-axial processors are constrained by the overall machine width and the spacing between the respective rotor housings. In turn, this inhibits any significant increase in the crop-processing capacity of twin-axial processors.